The present invention relates to topsheets for absorptive devices such as diapers, sanitary napkins, bed pads, incontinent pads, towels, bandages and the like, and more particularly, to absorptive structures which freely allow fluid to pass into the interior of an absorptive device but which tend to inhibit the reverse flow of fluid. A topsheet or facing sheet is the portion of an absorptive device which covers one face of the absorbent element of an absorptive device and which typically contacts the skin of the person using the absorptive device.
Absorptive devices are articles of manufacture designed to receive and retain fluid discharges from the wearer's body within an absorbent element of the absorptive device. Absorptive devices such as diapers, sanitary napkins, catamenial tampons, bed pads, incontinent pads, towels, bandages and the like are well known articles of commerce. In recent times, single use disposable absorptive devices have significantly replaced permanent absorptive devices which are designed to be laundered and reused. While the improved absorptive structure of the present invention can be used with reusable absorptive devices, it finds greatest utility when utilized with disposable absorptive devices and will be discussed in that context.
Disposable absorptive devices comprising an absorbent pad covered with a topsheet which contacts the body are well known. Covering the outer portion of the absorptive device with a moisture-resistant or fluid-impermeable backsheet to prevent absorbed fluids from leaking out of the absorptive device and soiling clothing, bed clothes, etc. is equally well known. The absorbent pad component of disposable absorptive devices can comprise well known materials such as creped cellulose wadding, air-laid felt, or the like. The fluid-impermeable backsheet can comprise any of various materials well known in the art such as polyethylene film.
One of the principle disadvantages of conventional absorptive devices is the maceration of the skin caused by prolonged contact with absorbed fluids. One especially common manifestation of this maceration is diaper rash generally occurring about the base of the trunk of infants. In order to minimize the effect of prolonged liquid contact with the skin, absorptive devices such as diapers have been produced with the body contacting topsheet thereof designed to exhibit a greater degree of surface dryness. For example, U.S. Pat. No. 3,327,625 issued to Johnson on Mar. 1, 1966, teaches the use of a hydrophobic material in the crotch area of the diaper to cause moisture to wick away from the skin of an infant wearer and thereby provide a substantially dry surface in contact with the infant's skin. U.S. Pat. No. Re. 26,151 issued to Duncan et al. on Jan. 31, 1967, teaches the use of porous, hydrophobic, nonwoven fabrics as topsheets. U.S. Pat. No. 2,916,037 issued to Hansen on Dec. 8, 1959, is a further example of the use of a nonwoven topsheet.
U.S. Pat. No. 3,814,191 issued to Kozak on June 4, 1974, attacks the problem of a wet topsheet in a manner slightly different from the use of hydrophobic nonwoven materials. Kozak suggests a topsheet of a non-fibrous, hydrophobic film which is provided with a plurality of valvular slits which restrict the reverse flow of liquid from the absorbent element of the device. U.S. Pat. No. 3,929,135, issued to Thompson on Dec. 30, 1975, suggests a topsheet of liquid-impermeable material provided with tapered capillaries, said capillaries having a base in the plane of the topsheet and an apex remote from the plane of said topsheet.
U.S. Pat. No. 3,934,588 issued to Mesek et al. on Jan. 27, 1976, suggests a topsheet provided with areas of preferential liquid flow surrounded by areas of increased water repellancy relative to the areas of preferential liquid flow. The areas of preferential liquid flow are, in preferred embodiments, in the form of thinned areas, areas of increased wettability or areas of normal wettability surrounded by water repellant borders. The preferential liquid flow areas are spread over at least the central portion of the facing layer to direct liquid to the absorbent pad.